[API] Test Runner: Stringify header keys, do not overwrite headers if set

Author: picandocodigo

api-spec-testing/test_file/action.rb

@@ -73,6 +73,8 @@ def execute(client, test = nil)
             if headers[:Authorization] == 'Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA=='
               headers.delete(:Authorization)
             end
+            # Stringify keys:
+            headers = headers.transform_keys(&:to_s)
             if ENV['QUIET'] == 'true'
               # todo: create a method on Elasticsearch::Client that can clone the client with new options
               Elasticsearch::Client.new(

elasticsearch-transport/lib/elasticsearch/transport/client.rb

@@ -208,6 +208,7 @@ def set_api_key
 
       def set_compatibility_header
         return unless ['1', 'true'].include?(ENV['ELASTIC_CLIENT_APIVERSIONING'])
+        return if instance_variable_get('@options').dig(:transport_options, :headers, 'Accept')
 
         add_header(
           {